With the advancement of information communication technologies, various wireless communication technologies have recently been developed. Among the wireless communication technologies, a wireless local area network (WLAN) is a technology whereby Internet access is possible in a wireless fashion in homes or businesses or in a region providing a specific service by using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
The IEEE 802.11n is a technical standard relatively recently introduced to overcome a limited data rate which has been considered as a drawback in the WLAN. The IEEE 802.11n is devised to increase network speed and reliability and to extend an operational distance of a wireless network. More specifically, the IEEE 802.11n supports a high throughput (HT), i.e., a data processing rate of up to above 540 Mbps, and is based on a multiple input and multiple output (MIMO) technique which uses multiple antennas in both a transmitter and a receiver to minimize a transmission error and to optimize a data rate.
Meanwhile, as the spread of a WLAN is activated, there appears an environment in which one AP provides service to a large number of non-AP stations. The characteristics of a WLAN that supporting this environment may be represented by a low data rate, low power, and wide coverage. To this end, devices operating within this WLAN environment may transmit and receive radio signals using a lower frequency band.
As a frequency of a low band is used, a channel bandwidth used to transmit and receive radio signals may become lower than the existing frequency of a high band. A change of the frequency band used to transmit and receive radio signals as described above requires a discussion on a new channel access method by a wireless apparatus.